Illumination device and image display apparatus

ABSTRACT

An illumination device includes: an excitation light source that emits excitation light having a first wavelength; a fluorescent substance that, when irradiated with the excitation light, emits light having a second wavelength longer than the first wavelength and transmits a part of the excitation light, and thereby multiplexes and emits the transmitted excitation light having the first wavelength and the emitted excitation light having the second wavelength; and a driving unit that moves an irradiation position of the excitation light in the fluorescent substance with the passage of time.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. JP 2010-137192 filed in the Japanese Patent Office on Jun. 16, 2010,the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an illumination device and an image displayapparatus, and more particularly, to an illumination device used as alight source of a projection type image display apparatus such as aprojector, and an image display apparatus including the illuminationdevice.

2. Description of the Related Art

In recent years, in regard to watching movies at home, a presentation ata meeting, or the like, the opportunities to use a projection-type imagedisplay apparatus, such as a projector, have been increasing. In such aprojector, as a light source, for example, a discharge type lamp, suchas a mercury lamp, having high brightness is generally used. Inaddition, with the recent progresses in the development techniques forsolid-state light emitting devices (for example, semiconductor lasers,light emitting diodes, or the like), there has been also suggested aprojector using the solid-state light emitting device (for example, seeJP-A-2009-277516).

The projector disclosed in JP-A-2009-277516 is a DLP (Digital LightProcessing: registered trademark) type projector. In such a type ofprojector, images are displayed in full color through a time divisiondisplay of approximately several thousand times per second for thedifferent colors.

The projector disclosed in P-A-2009-277516 has a light source devicethat includes a light emitting diode (excitation light source) thatemits blue light (excitation light), a transparent substrate provided atan emission side of the excitation light, and a motor that rotates thetransparent substrate in a plane orthogonal to an emission direction ofthe excitation light.

In the light source device disclosed in JP-A-2009-277516, a redfluorescent layer that emits red light by the irradiation of theexcitation light, a green fluorescent layer that emits green light bythe irradiation of the excitation light, and a region that transmits theexcitation light “as is” are formed at different regions on atransparent base. Therefore, in regard to the projector disclosed inJP-A-2009-277516, when the excitation light is emitted to thetransparent base rotating with a predetermined number of rotations, theblue light (excitation light), and red light and green light excited bythe excitation light are time-divisionally emitted from the light sourcedevice.

SUMMARY OF THE INVENTION

As described above, a projector not using a mercury lamp has beensuggested in the related art, and in such a projector, it is possible torealize a mercury-free projector in response to recent environmentalconcerns. In addition, in a case where for example, a solid-state lightemitting device such as a semiconductor laser and a light-emitting diodeis used as a light source, it has an advantage that durability is longerand a decrease in brightness is also lower compared to the mercury lamp.

However, the technique disclosed in JP-A-2009-277516 is only applicableto a light source device (illumination device), for example, a DLP(registered trademark) type projector or the like that time-divisionallyemits plural kinds of single-color light having wavelengths differingfrom each other. The technology may be not applicable to applicationswhere a light source device emitting white light is necessary, like a 3LCD (Liquid Crystal Display) type projector or the like.

Thus, it is desirable to provide a mercury-free illumination device thatis also applicable to various applications such as a 3 LCD typeprojector and an image display apparatus having the illumination device.

An illumination device according to an embodiment of the inventionincludes an excitation light source, a fluorescent substance, and adriving unit. A function of each section is as follows. The excitationlight source emits excitation light having a first wavelength. Whenbeing irradiated with the excitation light, the fluorescent substanceemits light having a second wavelength longer than the first wavelengthand transmits a part of the excitation light, and thereby multiplexesand emits the transmitted excitation light having the first wavelengthand the emitted excitation light having the second wavelength. Thedriving unit moves an irradiation position of the excitation light inthe fluorescent substance with the passage of time. In addition, theabove-described “wavelength” means a wavelength including not only asingle wavelength but also a predetermined wavelength band.

An image display apparatus according to another embodiment of theinvention includes a light source device section and an image projectionsection. A function of each section is as follows. The light sourcedevice section has the same configuration as that of the illuminationdevice of the above-described embodiment of the invention. The imageprojection section generates a predetermined image light by using thelight emitted from the light source device section and projects thegenerated image light to the outside.

According to the embodiment of the invention, when being irradiated withthe excitation light, the fluorescent substance emits light having awavelength (second wavelength) longer than the wavelength (firstwavelength) of the excitation light and transmits a part of theexcitation light, and thereby multiplexes and emits the transmittedexcitation light and light emitted from the fluorescent substance(hereinafter, referred to as “emission light”). That is, according tothe embodiment of the invention, light having a wavelength banddifferent from that of the excitation light and the emission light isemitted from the fluorescent substance. Therefore, according to theembodiment of the invention, in a case where the excitation light is setas blue light and the emission light is set as light (for example,yellow light or the like) including both red light and green light, itis possible to emit white light from the fluorescent substance.

As described above, according to the embodiment of the invention, byappropriately setting a combination of the first wavelength of theexcitation light and the second wavelength of the emission light, it ispossible to emit white light or the like from the fluorescent substance.Therefore, according to the embodiment of the invention, it is possibleto provide a mercury-free illumination device that is also applicable tovarious applications such as a 3 LCD type projector and an image displayapparatus having the illumination device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block configuration diagram illustrating an imagedisplay apparatus according to an embodiment of the invention;

FIGS. 2A to 2C are schematic configuration diagrams illustrating afluorescent member used for a light source device section (illuminationdevice);

FIG. 3 is a view illustrating a configuration example of a reflectivefilm used in a fluorescent member

FIG. 4 is a view illustrating a relationship between a transmittance ofthe reflective film used in the fluorescent member and a light incidenceangle;

FIG. 5 is a view illustrating a light emission state in a fluorescentsubstance and a light reflection state in a surface of the reflectivefilm; and

FIG. 6 is a view illustrating a spectral characteristic of emitted lightof the light source device section (illumination device) according tothe embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, description will be given to an example of an illuminationdevice and an image display apparatus having the same according to anembodiment of the invention with reference to accompanying drawings inthe following order. In addition, in this embodiment, a 3 LCD typeprojector utilizing a transmission type LCD optical modulation device isdescribed as an example of the image display apparatus, but theinvention is not limited thereto.

1. Configuration Example of Image Display Apparatus

2. Configuration Example of Light Source Device Section (IlluminationDevice)

3. Configuration Example of Fluorescent Member

4. Operation Example of Light Source Device Section

[1. Configuration Example of Image Display Apparatus]

FIG. 1 shows a configuration example of an image display apparatusaccording to an embodiment of the invention. In FIG. 1, for simplicityof explanation, only main portions that are operated when image light isprojected to the outside in the image display apparatus 10 of thisembodiment are mainly shown. In addition, in FIG. 1, a configurationexample of a 3 LCD type projector is shown, but the invention is notlimited thereto. The invention may also be applied to a 3 LCD typeprojector using a reflection-type LCD light modulation device.

The image display apparatus 10 includes a light source device section 1(illumination device) and an optical engine section 2 (image projectingsection). In addition, a configuration of the light source devicesection 1 will be described later.

The optical engine section 2 optically processes light (white light LWin this example) emitted from the light source device section 1 togenerate image light LI, and magnifies and projects the image light LIto, for example, an external screen. The optical engine section 2includes, for example, a spectral optical system 20, a 3 LCD opticalmodulation device (hereinafter, referred to as “a first LCD panel 21 tothird LCD panel 23”, respectively), a prism 24, and a projection opticalsystem 25. In addition, the configuration of the optical engine section2 is not limited to an example shown in FIG. 1 and may be appropriatelychanged, for example, according to application or the like. For example,various necessary optical devices may be appropriately disposed on anoptical path between each of sections.

In addition, in the optical engine section 2 of this example, the firstand third LCD panels 21 and 23 are disposed with light emitting surfacesthereof opposed to each other, and the second LCD panel 22 is disposedin a direction orthogonal to an opposing direction of the first andthird LCD panels 21 and 23. The prism 24 is disposed at a regionencompassed by light emitting surfaces of the first to third LCD panels21 to 23. In addition, in this example, the projection optical system 25is disposed at a position opposing a light emitting surface of thesecond LCD panel 22 with the prism 24 interposed therebetween. Inaddition, the spectral optical system 20 is provided at a light incidentside of the first to third LCD panels 21 to 23.

The spectral optical system 20 is configured by, for example, a dichroicmirror, a reflective mirror, or the like, disperses white light LWincident from the light source device section 1 into blue light LB,green light LG, and red light LR and emits light of each wavelengthcomponent to each corresponding LCD panel. In this example, the spectraloptical system 20 emits each of the dispersed blue light LB, green lightLG, and red light LR to the first LCD panel 21, the second LCD panel 22,and the third LCD panel 23, respectively.

Each of the first to third LCD panels 21 to 23 is configured by atransmissive LCD panel. Each of the LCD panels transmits or shields(modulates) the incident light with a liquid crystal cell unit bychanging an arrangement of liquid crystal molecules enclosed in a liquidcrystal cell (not shown) on the basis of a driving signal supplied froma panel drive section (not shown). Therefore, each of the LCD panelsemits light (modulated light) to the prism 24 with a predeterminedwavelength that is modulated.

The prism 24 multiplexes the modulated light of each wavelengthcomponent incident from the first to third LCD panels 21 to 23,respectively, and emits the multiplexed light, that is, image light LIto the projection optical system 25.

The projection optical system 25 magnifies and projects the image lightincident from the prism 24 onto a display surface of, for example, anexternal screen or the like.

[2. Configuration Example of Light Source Device Section 1]

Next, an internal configuration of the light source device section 1 ofthis embodiment will be described with reference to FIG. 1.

The light source device section 1 includes an excitation light source11, a first condensing optical system (first optical system), afluorescent member 13, a motor 14 (driving unit), and a secondcondensing optical system 15 (second optical system). In the lightsource device section 1 of this embodiment, the first condensing opticalsystem 12, the fluorescent member 13, and the second condensing opticalsystem 15 are disposed in this order from an emission opening of theexcitation light L of the excitation light source 11. At this time, thefirst condensing optical system 12, a layer-shaped fluorescent substance32 (hereinafter, referred to as “fluorescent layer 32”) that isdescribed later, in the fluorescent member 13, and the second condensingoptical system 15 are disposed on an optical path of the excitationlight L.

The excitation light source 11 is configured by a solid-state lightemitting device that emits light of a predetermined wavelength (a firstwavelength). In this example, as the excitation light source 11, a bluelaser emitting blue light with a wavelength of 445 nm is used. Inaddition, in this embodiment, a wavelength of the excitation light Lincident to the fluorescent layer 32 is set to a wavelength shorter thanthat of light emitted from the fluorescent layer 32 that is describedlater, in the fluorescent member 13.

In addition, in a case where as the excitation light source 11, a bluelaser is used, it may be configured to obtain excitation light L with apredetermined output by one blue laser, and it may be configured tomultiplex emitted light from each of plural blue lasers and obtainexcitation light L with a predetermined output. In addition, awavelength of the blue light (excitation light L) is not limited to 445nm, and it is possible to use any wavelength as long as the wavelengthis within a wavelength band of light called blue light.

The first condensing optical system 12 condenses the excitation light Lemitted from the excitation light source 11 and emits the condensedexcitation light L (hereinafter, referred to as “condensed light”) tothe fluorescent member 13. At this time, for example, parameters such aslens configuration, focal point distance, and alignment position of thefirst condensing optical system 12 are designed so that the condensedlight is incident to the fluorescent member 13 with a predeterminedincidence angle θ. In addition, the incidence angle θ of the condensedlight is appropriately set corresponding to a transmittingcharacteristic (incidence angle dependency of a transmittance) of areflective film 31, which is described later, in the fluorescent member13.

In addition, when the spot diameter of the excitation light L in thefirst condensing optical system 12 is focused, it is possible toirradiate highly dense excitation light L to the fluorescent member 13.Therefore, when the spot of the excitation light L is excessivelyfocused, excitation light L having a light amount larger than thatnecessary for allowing fluorescent atoms in an irradiation region toemit light is irradiated. In this case, in regard to the irradiationregion, since the light quantity not contributing to the light emissionof the fluorescent atoms is increased, a ratio of the light emissionamount to the light amount of the incident excitation light L isdecreased, whereby a light emission efficiency of the fluorescent layer32 is decreased. Therefore, in this embodiment, the configuration of thefirst condensing optical system 12 is designed so that the spot diameterof the condensed light becomes a diameter not decreasing the lightemission efficiency.

Conversely, when the spot diameter of the condensed light excessivelybroadens, the broadening of the emission light from the fluorescentmember 13 is increased. In this case, the spot diameter of the condensedlight may be controlled so as not to broaden by the first condensingoptical system 12, or a configuration where the broadened emission lightis converted into parallel light having a predetermined diameter by thesecond condensing optical system 15 may be considered.

The fluorescent member 13 emits light with a predetermined wavelengthband (second wavelength) by the excitation light L (blue light) incidentthereto via the first condensing optical system 12 and transmits a partof the excitation light L. In this example, since the light incident tothe optical engine section 2 is set as white light LW, the fluorescentmember 13 emits, by the excitation light L, light with a wavelength band(approximately 480 to 680 nm) including green light and red light. Inthis embodiment, the emission light with a wavelength band includinggreen light and red light and a part of the excitation light L (bluelight) that is transmitted through the fluorescent member 13 aremultiplexed and white light LW is generated. In addition, detailedconfiguration of the fluorescent member 13 will be described later.

The motor 14 rotatably drives the fluorescent member 13 with apredetermined number of rotations. At this time, the motor 14 drives thefluorescent member 13 so that the fluorescent member 13 rotates in adirection along a plane (an irradiation plane of the excitation light Lof the fluorescent layer 32 described later) orthogonal to anirradiation direction of the excitation light L.

A rotational shaft 14 a of the motor 14 is attached to the center of atransparent substrate 30, which is described later, of the fluorescentmember 13, and the transparent substrate is fixed to the rotationalshaft 14 a by a fixing hub 14 b. The fluorescent member 13 is rotatablydriven by the motor 14, such that the irradiation position of theexcitation light L in the fluorescent member 13 is moved with thepassage of time at a speed corresponding to the number of rotations in aplane orthogonal to the irradiation direction of the excitation light L.

As described above, the fluorescent member 13 is rotatably driven by themotor 14 and the irradiation position of the excitation light in thefluorescent member 13 is moved with the passage of time, such that it ispossible to suppress an increase in the temperature at the irradiationposition and it is possible to prevent the light emission efficiency ofthe fluorescent layer 32 from being decreased. In addition, it takessome time (for example, several nsec) for fluorescent atoms to absorbthe excitation light L and to emit light, and even when the nextexcitation light L is emitted to the fluorescent atoms for theexcitation period, the atoms do not emit light. However, according tothis embodiment, the irradiation position of the excitation light L inthe fluorescent member 13 is moved with the passage of time, such thatthe fluorescent atoms not excited are sequentially disposed at theirradiation position of the excitation light L and thereby it ispossible to allow the fluorescent layer 32 to efficiently emit light.

In addition, in this embodiment, an example where the fluorescent member13 is rotatably driven by the motor 14 is illustrated. However, theinvention is not limited thereto and may be configured in any manner aslong as the irradiation position of the excitation light L in thefluorescent member is moved with the passage of time. For example, theirradiation position of the excitation light L may be moved with thepassage of time by making the fluorescent member 13 lineally reciprocatein a predetermined direction in a plane (in an irradiation plane of theexcitation light L in a fluorescent layer 32 described later) orthogonalto the irradiation direction of the excitation light L. In addition, theirradiation position of the excitation light L may be moved with thepassage of time by fixing the fluorescent member 13 and by relativelymoving the excitation light source 11 with respect to the fluorescentmember 13.

The second condensing optical system 15 condenses light (white light LW)emitted from the fluorescent member 13 and converts it into parallellight. Then, the second condensing optical system 15 guides the parallellight to the spectral optical system 20 of the optical engine section 2.In addition, the second condensing optical system 15 may be configuredby a single collimator lens or may be configured to convert incidentlight into parallel light by using plural lenses. In addition, since theemission light from the fluorescent member 13 is light that expands in alambertian (uniform diffusion) shape, it is preferable that the distancebetween the second condensing optical system 15 and the fluorescentmember 13 (more specifically fluorescent layer 32 described later) is asshort as possible.

In addition, in this embodiment, an example where the first condensingoptical system 12 and the second condensing optical system 15 areprovided in the light source device section 1 is described, but theinvention is not limited thereto. For example, in a case where the lightsource device section 1 of this embodiment is applied to an applicationwhere even when the output of the emitted light from the light sourcedevice 1 is small, this does not cause a problem, and either the firstcondensing optical system 12 or the second condensing optical system 15or both of them may be not provided.

[3. Configuration Example of Fluorescent Member]

Next, a more detailed configuration of the fluorescent member 13 will bedescribed with reference to FIGS. 2A to 2C. In addition, FIG. 2A shows afront view of the fluorescent member 13 seen from the second condensingoptical system 15 side, FIG. 2B shows a cross sectional view taken alonga line A-A of FIG. 2A, and FIG. 2C shows a front view of the fluorescentmember 13 seen from the first condensing optical system 12 side.

The fluorescent member 13 includes a disk-shaped transparent substrate30, a reflective film 31 and a fluorescent layer 32 (fluorescentsubstance) formed on one surface of the transparent substrate 30, and areflection prevention film 33 formed on the other surface of thetransparent substrate 30.

The transparent substrate 30 is formed from a transparent material suchas glass and transparent resin. In addition, a size such as thethickness of the transparent substrate 30 is appropriately set inconsideration of, for example, the necessary transmittance, strength, orthe like.

The reflective film 31, as shown in FIG. 2A, is formed on one surface ofthe transparent substrate 30 with a doughnut shape. The doughnut-shapedreflective film 31 is disposed on the transparent substrate 30 in amanner such that the reflective film 31 and the transparent substrate 30are concentric to each other. In addition, a width of the reflectivefilm 31 in the radial direction thereof is set to a value larger thanthe spot size of the excitation light L (condensed light) condensed bythe first condensing optical system 12.

In addition, the reflective film 31 not only reflects the light(emission light) excited at the fluorescent layer 32 to the secondcondensing optical system 15 side, but also reflects the excitationlight L (blue light) scattered in and reflected from the fluorescentlayer 32 to the second condensing optical system 15 side.

Here, FIG. 3 shows one configuration example of the reflective film 31.The reflective film 31 is formed by alternately laminating a firstdielectric layer 31 a formed from, for example, an SiO2 layer, a MgF2layer, or the like and a second dielectric layer 31 b formed from, forexample, a TiO2 layer, a Ta2O3 layer, or the like on the transparentsubstrate 30. Specifically, the reflective film 31 may be configured bya dichroic mirror (dichroic film). In addition, the lamination count ofeach of the first dielectric layer 31 a and the second dielectric layer31 b may generally be several layers to several tens of layers. Inaddition, the first dielectric layer 31 a and the second dielectriclayer 31 b are formed by, for example, a vapor-deposition method, asputtering method, or the like.

In a case where the reflective film 31 is configured by a dichroicmirror as shown in FIG. 3, by the adjustment of a lamination count ofeach dielectric layer, a thickness of each dielectric layer, a formingmaterial of each dielectric layer, or the like, it is possible to easilyset an incidence angle dependency of a transmittance (reflectance) oflight incident to the reflective film 31. FIG. 4 shows an example of theincidence angle dependency of an optical transmittance of the reflectivefilm 31 used in this embodiment. In FIG. 4, a horizontal axis representsa wavelength of incident light and a vertical axis represents atransmittance.

In the example shown in FIG. 4, the reflective film 31 is designed toselectively reflect light with a wavelength band (a wavelength band ofapproximately 480 to 680 nm) including red light and green lightregardless of incidence angles θ thereof. Therefore, with respect tolight (emission light from the fluorescent layer 32) with a wavelengthband including red light and green light, the transmittance becomesapproximately zero regardless of the incidence angle θ of the light.That is, light with a wavelength band including red light and greenlight is totally reflected from the reflective film 31, regardless ofthe incidence angle θ thereof.

On the other hand, with respect to blue light (excitation light L) witha wavelength of 445 nm, the reflective film 31 is designed such thatwhen the incidence angle θ thereof is approximately 20° or less, ittransmits the blue light, and when the incidence angle θ thereof islarger than approximately 20°, it reflects the blue light. Therefore, asshown in FIG. 4, at a wavelength of 445 nm (thick broken line) of theblue light (excitation light L), when the incidence θ of the light is 0°(solid line) and 15° (broken line), the transmittance becomes large. Inaddition, when the incidence θ of the blue light is 30° (one dottedline), 45° (dotted line), and 60° (two dotted line), the transmittanceat a wavelength of 445 nm becomes small. That is, in the excitationlight L that is scattered in and reflected from the fluorescent layer32, an excitation light component incident to the reflective film 31 atan incidence angle θ larger than approximately 20° is reflected from thereflective film 31 in a direction toward the second condensing opticalsystem 15.

In addition, as described above, the configuration of the firstcondensing optical system 12 is designed according to the incidenceangle dependency of transmittance of the reflective film 31. Forexample, in a case where the reflective film 31 has the incidence angledependency of transmittance shown in FIG. 4, so as not to decrease theusage efficiency of the excitation light L, the first condensing opticalsystem 12 is designed such that the incidence angle θ of the condensedexcitation light L becomes 20° or less.

In addition, the fluorescent layer 32 is a layer-shaped fluorescentsubstance that emits light with a predetermined wavelength band when theexcitation light L is emitted thereto. In this embodiment, transmittedlight of the excitation light L and emission light in the fluorescentlayer 32 are multiplexed and white light LW is generated, such that asthe fluorescent layer 32, for example, a YAG (Yttrium AluminumGarnet)-based fluorescent material or the like is used. In this case,when blue excitation light L is incident to the fluorescent layer 32,the fluorescent layer 32 emits light with a wavelength band of 480 to680 nm (yellow light). In addition, the fluorescent layer 32 may beconfigured by any material as long as a film can emit light with awavelength band including red light and green light, but it ispreferable that the YAG-based fluorescent material is used, from theview point of light-emitting efficiency and heat resistance.

The fluorescent layer 32 is formed by applying a predeterminedfluorescent agent obtained by mixing a fluorescent material and a binderon the reflective film 31. In the example shown in FIGS. 2A to 2C, thefluorescent layer is formed so as to cover the entire surface of thereflective film 31, such that the surface shape of the fluorescent layer32 become a doughnut shape. In addition, the fluorescent layer 32 may beformed only at a region where the excitation light L is emitted thereto,such that the shape of the fluorescent layer 32 is not limited to theexample shown in FIGS. 2A to 2C, and for example, a width of thefluorescent layer 32 in a radial direction may be narrower than that ofthe reflective film 31.

In addition, in regard to the fluorescent layer 32, a light emissionamount, and a transmission amount of the excitation light L may beadjusted by a thickness of the fluorescent layer 32, a density(contained amount) of a fluorescent substance, or the like. Therefore,in this embodiment, the thickness of the fluorescent layer 32, thedensity of the fluorescent substance, or the like is adjusted so thatthe emitted light from the light source device section 1 becomes whitelight.

The reflection prevention film 33 is provided on a surface of thetransparent substrate 30 at an incidence side of the excitation light Land prevents the reflection of the excitation light L, which isgenerated at the incidence plane of the condensed light when thecondensed light of the excitation light L is incident to the fluorescentmember 13. Therefore, the usage efficiency of the excitation light L maybe improved.

In addition, in this embodiment, an example where the reflective film 31and the reflection prevention film 33 are provided in the fluorescentmember 13 is described, but the invention is not limited thereto. Forexample, in a case where the light source device section 1 of thisembodiment is applied to an application where even when the output ofthe emitted light is small, this does not cause a problem, either thereflective film 31 or the reflection prevention film 33 or both of themmay be not provided. In addition, in the fluorescent member 13 of theabove-described embodiment, an example where the layer-shapedfluorescent substance (fluorescent layer 32) is formed on the substrate30 via the reflective film 31 is described, but the invention is notlimited thereto. For example, in a case where the fluorescent substanceis configured by a plate-shaped member having sufficient strength, thetransparent substrate 30 may not be provided.

[4. Operation Example of Light Source Device Section]

FIG. 5 shows an operational state of the light source device section 1of this embodiment. In the light source device section 1 of thisembodiment, the excitation light L (blue light in this example) emittedfrom the excitation light source 11 is first condensed at the firstcondensing optical system 12. Subsequently, the condensed light (thecondensed excitation light L) is incident to the fluorescent member 13from the reflection prevention film 33 side of the fluorescent member 13at a predetermined incidence angle θ. In addition, in this embodiment,the fluorescent member 13 is irradiated with the condensed light in astate where the fluorescent member 13 is rotating with a predeterminednumber of rotations by the motor 14.

The condensed light incident to the fluorescent member 13 is transmittedthrough the reflection prevention film 33, the transparent substrate 30,and the reflective film 31, and is incident to the fluorescent layer 32.In addition, as described above, since the reflective film 31 isdesigned to transmit the excitation light L with a predeterminedincidence angle θ or less, the condensed light incident to thefluorescent member 13 is not reflected from the reflective film 31.

Subsequently, when the condensed light (excitation light L) is incidentto the fluorescent layer 32, a part of the condensed light (excitationlight L) is transmitted through the fluorescent layer 32 and theremainder thereof is mainly absorbed by the fluorescent layer 32. Due tothe absorbed excitation light L, the fluorescent layer 32 is excited,and light (in this example, yellow light including red light and greenlight) with a predetermined wavelength band is emitted from thefluorescent layer 32. As a result, a transmitted component of theexcitation light L and the emission light from the fluorescent layer 32are multiplexed and white light is emitted from the fluorescent layer32.

In addition, at this time, the emission light of the fluorescent layer32 is not only emitted in a direction toward the second condensingoptical system 15, but is also emitted in a direction toward thetransparent substrate 30. In addition, a part of the excitation light Lincident to the fluorescent layer 32 is also scattered and reflectedinside the fluorescent layer 32 in a direction toward the transparentsubstrate 30. However, in the fluorescent member 13 of this embodiment,as described above, since the reflective film 31 is provided between thetransparent substrate 30 and the fluorescent layer 32, the emissionlight and the excitation light component emitted in a direction towardthe transparent substrate 30 is reflected by the reflective film 31 in adirection toward the second condensing optical system 15. At this time,the excitation light component reflected from the reflective film 31 isabsorbed in the fluorescent layer 32 and further allows the fluorescentlayer 32 to emit light. Therefore, like this embodiment, in a case wherethe reflective film 31 is provided between the transparent substrate 30and the fluorescent layer 32, it is possible to increase the usageefficiency of the excitation light L and it is possible to increase thelight amount of the emission light.

In addition, in practice, the inventor of the invention set parametersof each section of the light source device section 1 as follows, andexamined a spectral characteristic of the emitted light from the lightsource device section 1.

Wavelength of the excitation light source 11 (blue laser): 445 nm

Condensing diameter of excitation light L: 1 mm

Incidence angle θ of excitation light L: 20° or less

Number of rotations of the fluorescent member 13: 3000 rpm

Distance between the second condensing optical system 15 and thefluorescent layer 32: 1 mm or less

Forming material of the transparent substrate 30: Glass

Diameter of the transparent substrate 30: 30 mm

Transmission characteristics of the reflective film 31: Characteristicshown in FIG. 4

Forming material of the fluorescent layer 32: A YAG-based fluorescentsubstance

Thickness of the fluorescent layer 32: 50 μm

Width of the fluorescent layer 32: 5 mm

FIG. 6 shows a spectral characteristic of an emitted light from thelight source device section 1, which is obtained under theabove-described conditions. In addition, in the characteristic shown inFIG. 6, a horizontal axis represents a wavelength, and a vertical axisrepresents intensity (any unit) of the emitted light. As can be seenfrom FIG. 6, under the condition, it can be seen that a light component(blue light component) near a wavelength of 445 nm and a light componentwith a wavelength ranging from approximately 480 to 680 nm, that is, alight component including a red light component and a green lightcomponent are included in the emitted light. From this, it can also beseen that white light LW is emitted from the light source device section1 of this embodiment.

As described above, it is possible to emit the white light from thelight source device section 1 by using a solid-state light emittingdevice. Therefore, this embodiment may be applied for an applicationwhere a light source device emitting white light is necessary, forexample, like in a 3 LCD type projector. That is, in this embodiment, itis possible to provide a mercury-free light source device section 1(illumination device), which can be applied for various applications,and an image display apparatus 10 having the same.

In the light source device section 1 of this embodiment, it is notnecessary to use a mercury lamp, such that it is possible to cope with arecent environmental problem. In addition, according to this embodiment,it is possible to provide a light source device section 1 of whichdurability is longer and decrease in brightness is also lower comparedto the mercury lamp, and an image display apparatus 10. In addition,like in this embodiment, when a solid-state light emitting device isused in the excitation light source 11, a lighting time may be shortenedcompared to the mercury lamp.

In addition, in a case where a semiconductor laser is used as theexcitation light source 11 like in the light source device section 1 ofthis embodiment, light with a sufficiently high brightness may beemitted compared to a solid-state light source such as an LED (LightEmitting Diode) and thereby it is possible to realize a high brightnesslight source. In addition, like in this embodiment, a configurationwhere the fluorescent layer 32 is made to emit light by using a bluelight laser to generate white light LW is cheaper than a configurationwhere solid-state light sources for red light, green light and bluelight are separately prepared to generate white light.

In addition, in this embodiment, a 3 LCD type projector is described asan example of the light source device section 1 (illumination device),but the invention is not limited thereto. The invention may be appliedto any image display apparatus where white light is necessary and thesame effect may be obtained.

In the embodiment, there is described an example where the emitted lightof the light source device section 1 (illumination device) is set aswhite light, but the invention is not limited thereto. For example, asthe emitted light, blue light may be used for an application where cyanlight (or magenta light) is necessary as the excitation light L, or thefluorescent layer 32 may be formed by a fluorescent material that emitsonly green light (or red light). That is, according to a necessarywavelength (color) of the emitted light, a combination of the wavelengthof the excitation light L and the material for forming the fluorescentlayer 32 may be appropriately selected.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An illumination device comprising: an excitation light source thatemits excitation light having a first wavelength; a fluorescentsubstance that, when irradiated with the excitation light, emits lighthaving a second wavelength longer than the first wavelength andtransmits a part of the excitation light, and thereby multiplexes andemits the transmitted excitation light having the first wavelength andthe emitted excitation light having the second wavelength; and a drivingunit that moves an irradiation position of the excitation light in thefluorescent substance with the passage of time.
 2. The illuminationdevice according to claim 1, further comprising: a reflective film thatis provided at an incidence side of the excitation light of thefluorescent substance and selectively reflects the light emitted fromthe fluorescent substance.
 3. The illumination device according to claim2, wherein the reflective film is a film that transmits the excitationlight with an incidence angle of a predetermined angle or less.
 4. Theillumination device according to claim 3, further comprising: a firstoptical system that condenses the excitation light such that theincidence angle of the excitation light to the reflective film becomesthe predetermined angle or less, and that is provided on an optical pathbetween the reflective film and the excitation light source.
 5. Theillumination device according to claim 1, further comprising: a secondoptical system that converts the light emitted from the fluorescentsubstance into parallel light.
 6. The illumination device according toclaim 1, further comprising: a reflection preventing film that isprovided at an incidence side of the excitation light of the fluorescentsubstance and prevents the excitation light from being reflected.
 7. Theillumination device according to claim 1, wherein the first wavelengthis a blue wavelength, and the second wavelength is a wavelength bandincluding a red wavelength and a green wavelength.
 8. The illuminationdevice according to claim 1, wherein the driving unit moves thefluorescent substance to a predetermined direction in an irradiationsurface of the excitation light of the fluorescent substance.
 9. Animage display apparatus comprising: a light source device sectionincluding an excitation light source that emits excitation light havinga first wavelength, a fluorescent substance that, when irradiated withthe excitation light, emits light having a second wavelength longer thanthe first wavelength and transmits a part of the excitation light, andthereby multiplexes and emits the transmitted excitation light havingthe first wavelength and the emitted excitation light having the secondwavelength, and a driving unit that moves an irradiation position of theexcitation light in the fluorescent substance with the passage of time;and an image projection section that generates a predetermined imagelight by using the light emitted from the light source device sectionand projects the generated image light to the outside.